(MI_Metadata)fileIdentifier: gov.noaa.csc.maps:me2012_megis_aroostook_m2581language: eng; USAcharacterSet: (MD_CharacterSetCode) utf8hierarchyLevel: (MD_ScopeCode) datasetcontact: (CI_ResponsibleParty)individualName: Mike SutherlandorganisationName: DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of CommercecontactInfo: (CI_Contact)phone: (CI_Telephone)voice: 303-497-6120facsimile: 303-497-6513address: (CI_Address)deliveryPoint: NOAA/NESDIS/NGDC E/GC1 325 Broadwaycity: BoulderadministrativeArea: COpostalCode: 80305-3328country: USAelectronicMailAddress: mike.sutherland@noaa.govhoursOfService: 7:30am-5:00pm Mountainrole: (CI_RoleCode) authordateStamp: 2013-11-19metadataStandardName: ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded DatametadataStandardVersion: ISO 19115-2:2009(E)return to topspatialRepresentationInfo: (MD_VectorSpatialRepresentation)geometricObjects: (MD_GeometricObjects)geometricObjectType: (MD_GeometricObjectTypeCode) pointreturn to topreferenceSystemInfo: (MD_ReferenceSystem)referenceSystemIdentifier: (RS_Identifier)authority: (CI_Citation)title: North American Datum 1983alternateTitle: NAD83date: (CI_Date)date: 2007-01-19dateType: (CI_DateTypeCode) revisioncitedResponsibleParty: (CI_ResponsibleParty)organisationName: contactInfo: (CI_Contact)onlineResource: (CI_OnlineResource)linkage: http://www.epsg-registry.org/export.htm?gml=urn:ogc:def:crs:EPSG::4269name: NAD83description: Link to Geographic Markup Language (GML) description of reference system.function: (CI_OnLineFunctionCode) informationrole: (CI_RoleCode) resourceProvidercitedResponsibleParty: (CI_ResponsibleParty)organisationName: European Petroleum Survey GroupcontactInfo: (CI_Contact)onlineResource: (CI_OnlineResource)linkage: http://www.epsg-registry.org/name: European Petroleum Survey Group Geodetic Parameter Registrydescription: Registry that accesses the EPSG Geodetic Parameter Dataset, which is a structured dataset of Coordinate Reference Systems and Coordinate Transformations.function: (CI_OnLineFunctionCode) searchrole: (CI_RoleCode) publishercode: urn:ogc:def:crs:EPSG::4269return to topreferenceSystemInfo: (MD_ReferenceSystem)referenceSystemIdentifier: (RS_Identifier)code: Ellipsoid in MeterscodeSpace: Local Vertical Referencereturn to topidentificationInfo: (MD_DataIdentification)citation: (CI_Citation)title: 2012 MEGIS Topographic Lidar: Statewide Lidar Project Area 1 (Aroostook), Mainedate: (CI_Date)date: 2013-10-01dateType: (CI_DateTypeCode) publicationcitedResponsibleParty: (CI_ResponsibleParty)organisationName: DOC/NOAA/NOS/OCM > Office for Coastal Management, National Ocean Service, National Oceanic and Atmospheric Administration, U.S. Department of CommercecontactInfo: (CI_Contact)phone: (CI_Telephone)voice: 843-740-1200address: (CI_Address)deliveryPoint: 2234 South Hobson Ave.city: CharlestonadministrativeArea: SCpostalCode: 29405-2413electronicMailAddress: coastal.info@noaa.govonlineResource: (CI_OnlineResource)linkage: http://coast.noaa.govrole: (CI_RoleCode) originatorcitedResponsibleParty: (CI_ResponsibleParty)organisationName: Maine GeoLibrary Board (MEGIS)role: (CI_RoleCode) originatorcitedResponsibleParty: (CI_ResponsibleParty)organisationName: State of Maine Office of Information Technology (MEOIT)role: (CI_RoleCode) originatorcitedResponsibleParty: (CI_ResponsibleParty)organisationName: DOC/NOAA/NOS/OCM > Office for Coastal Management, National Ocean Service, National Oceanic and Atmospheric Administration, U.S. Department of CommercecontactInfo: (CI_Contact)phone: (CI_Telephone)voice: 843-740-1200address: (CI_Address)deliveryPoint: 2234 South Hobson Ave.city: CharlestonadministrativeArea: SCpostalCode: 29405-2413electronicMailAddress: coastal.info@noaa.govonlineResource: (CI_OnlineResource)linkage: http://coast.noaa.govrole: (CI_RoleCode) publisherpresentationForm: (CI_PresentationFormCode) imageDigitalabstract: LiDAR data is a remotely sensed high resolution elevation data collected by an airborne platform. The LiDAR sensor uses a combination of laser range finding, GPS positioning, and inertial measurement technologies. The LiDAR systems collect data point clouds that are used to produce highly detailed Digital Elevation Models (DEMs) of the earth's terrain, man-made structures, and vegetation. The work order required the LiDAR data to be collected at a nominal pulse spacing (NPS) of 1.5 meter. The final products include first, last, and at least one intermediate return LAS, full classified LAS and one (1) meter pixel raster DEMs of the bare-earth surface delivered in Esri 10 ArcGrid format.purpose: This work order consisted of LiDAR acquisition and processing for The Maine GeoLibrary Board (MEGIS) for three areas of the Maine Statewides Lidar Project, which is included within the Maine Statewide Orthoimagery Program. This metadata record is for Area 1 (also known as Aroostook) only. The work order required new LiDAR to be collected at a nominal post spacing of 1.5-meter during Spring 2012 and processed according the USGS LiDAR Guidelines and Base Specifications version13. The LiDAR data was collected to meet a vertical accuracy requirement of 12.5 cm (0.41 ft) RMSE. The LiDAR data was provided in 1,500 meters x 1,500 meters tiles in the UTM19 projection. The 1,500 meters x 1,500 meters LiDAR tile file name was derived from the southwest corner of each tile. The tiles are named based on the US National Grid. The enhanced lidar data will provide support multi-use applications, including homeland security, emergency management, economic development, and the business of government.status: (MD_ProgressCode) completedpointOfContact: (CI_ResponsibleParty)organisationName: State of Maine, Office of Information TechnologypositionName: State GIS Manager, Maine Office of GIScontactInfo: (CI_Contact)phone: (CI_Telephone)voice: (207)215-5530address: (CI_Address)deliveryPoint: State House Station 174, 264 Civic Center Drivecity: AugustaadministrativeArea: MEpostalCode: 04333-0174country: USArole: (CI_RoleCode) pointOfContactresourceMaintenance: (MD_MaintenanceInformation)maintenanceAndUpdateFrequency: (MD_MaintenanceFrequencyCode) asNeededgraphicOverview: (MD_BrowseGraphic)fileName: ftp://csc.noaa.gov/pub/DigitalCoast/lidar1_z/geoid12a/data/2581/supplemental/me2012_megis_aroostook_footprint12.KMZfileDescription: This kmz file shows the extent of coverage for the 2012 MEGIS Maine Statewide Lidar, Areas 1 lidar data set.fileType: kmzdescriptiveKeywords: (MD_Keywords)keyword: Topography/Bathymetrykeyword: Elevationkeyword: LiDARkeyword: Light Detection and Rangingkeyword: LAZkeyword: Remote Sensingtype: (MD_KeywordTypeCode) themethesaurusName: (CI_Citation)title: nonedate: descriptiveKeywords: (MD_Keywords)keyword: USkeyword: Mainekeyword: Aroostook Countytype: (MD_KeywordTypeCode) placethesaurusName: (CI_Citation)title: Nonedate: resourceConstraints: (MD_Constraints)useLimitation: These data depict the elevations at the time of the survey and are only accurate for that time. Users should be aware that temporal changes may have occurred since this data set was collected and some parts of this data may no longer represent actual surface conditions. Users should not use this data for critical applications without a full awareness of its limitations. Any conclusions drawn from analysis of this information are not the responsibility of NOAA or any of its partners. These data are NOT to be used for navigational purposes.resourceConstraints: (MD_LegalConstraints)useLimitation: While every effort has been made to ensure that these data are accurate and reliable within the limits of the current state of the art, NOAA cannot assume liability for any damages caused by any errors or omissions in the data, nor as a result of the failure of the data to function on a particular system. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.aggregationInfo: (MD_AggregateInformation)aggregateDataSetName: (CI_Citation)title: Lidar Final Reportdate: citedResponsibleParty: (CI_ResponsibleParty)positionName: Citation URLcontactInfo: (CI_Contact)onlineResource: (CI_OnlineResource)linkage: ftp://csc.noaa.gov/pub/DigitalCoast/lidar1_z/geoid12a/data/2581/supplemental/me2012_megis_aroostook_lidarreport.pdfname: Lidar Final Reportdescription: function: (CI_OnLineFunctionCode) informationrole: associationType: (DS_AssociationTypeCode) crossReferencespatialRepresentationType: (MD_SpatialRepresentationTypeCode) vectorlanguage: eng; USAtopicCategory: (MD_TopicCategoryCode) elevationextent: (EX_Extent)geographicElement: (EX_GeographicBoundingBox)westBoundLongitude: -68.710074eastBoundLongitude: -67.765333southBoundLatitude: 45.980887northBoundLatitude: 47.344577temporalElement: (EX_TemporalExtent)extent: TimePeriod: beginPosition: 2012-05-03endPosition: 2012-05-04temporalElement: (EX_TemporalExtent)extent: TimePeriod: beginPosition: 2012-05-06endPosition: 2012-05-07temporalElement: (EX_TemporalExtent)extent: TimeInstant: timePosition: 2012-05-12return to topdistributionInfo: (MD_Distribution)distributionFormat: (MD_Format)name: LAZversion: distributor: (MD_Distributor)distributorContact: (CI_ResponsibleParty)organisationName: DOC/NOAA/NOS/OCM > Office for Coastal Management, National Ocean Service, National Oceanic and Atmospheric Administration, U.S. Department of CommercecontactInfo: (CI_Contact)phone: (CI_Telephone)voice: 843-740-1200address: (CI_Address)deliveryPoint: 2234 South Hobson Ave.city: CharlestonadministrativeArea: SCpostalCode: 29405-2413electronicMailAddress: coastal.info@noaa.govonlineResource: (CI_OnlineResource)linkage: http://coast.noaa.govrole: (CI_RoleCode) distributordistributionOrderProcess: (MD_StandardOrderProcess)orderingInstructions: The National Geophysical Data Center serves as the archive for this LIDAR data. NGDC should only be contacted for this data if it cannot be obtained from
NOAA Coastal Services Center.distributor: (MD_Distributor)distributorContact: (CI_ResponsibleParty)individualName: Mike SutherlandorganisationName: DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of CommercecontactInfo: (CI_Contact)phone: (CI_Telephone)voice: 303-497-6120facsimile: 303-497-6513address: (CI_Address)deliveryPoint: NOAA/NESDIS/NGDC E/GC1 325 Broadwaycity: BoulderadministrativeArea: COpostalCode: 80305-3328country: USAelectronicMailAddress: mike.sutherland@noaa.govhoursOfService: 7:30am-5:00pm Mountainrole: (CI_RoleCode) distributordistributionOrderProcess: (MD_StandardOrderProcess)orderingInstructions: The National Geophysical Data Center serves as the archive for this LIDAR dataset. NGDC should only be contacted for the data if it cannot be obtained from
NOAA Coastal Services Center.return to topdataQualityInfo: (DQ_DataQuality)scope: (DQ_Scope)level: (MD_ScopeCode) datasetreport: (DQ_AbsoluteExternalPositionalAccuracy)nameOfMeasure: Horizontal Positional Accuracy ReportevaluationMethodDescription: Horizontal accuracy is at the 95% confidence level using RMSE(r) x 1.7308 as defined by the FGDC Geospatial Positional Accuracy Standards, Part 3: NSSDAresult: report: (DQ_AbsoluteExternalPositionalAccuracy)nameOfMeasure: Horizontal Positional AccuracymeasureDescription: LiDAR system calibration is available in the project report.result: (DQ_QuantitativeResult)valueUnit: BaseUnit: identifier: metersunitsSystem: value: Record: 0.250report: (DQ_AbsoluteExternalPositionalAccuracy)nameOfMeasure: Vertical Positional Accuracy ReportevaluationMethodDescription: Lidar Data Tested 0.07 meters at 95% confidence level. The data collected under this Task Order meets the National Standard for Spatial Database Accuracy (NSSDA) accuracy standards. The NSSDA standards specify that vertical accuracy be reported at the 95 percent confidence level for data tested by an independent source of higher accuracy. (http://www.fgdc.gov/standards/projects/FGDC-standards-projects/accuracy/part3/index_html)result: report: (DQ_AbsoluteExternalPositionalAccuracy)nameOfMeasure: Vertical Positional AccuracymeasureDescription: The LiDAR collected for this task order was tested to meet a vertical accuracy of 0.036 m Root Mean Squared (RMSE).result: (DQ_QuantitativeResult)valueUnit: BaseUnit: identifier: metersunitsSystem: value: Record: 0.07report: (DQ_CompletenessCommission)evaluationMethodDescription: The LiDAR data is visually inspected by Woolpert, Inc. for completeness to ensure that are no gaps between flight linesresult: report: (DQ_ConceptualConsistency)measureDescription: All formatted data are validated using commercial GIS software to ensure proper formatting and loading prior to delivery.result: lineage: (LI_Lineage)processStep: (LE_ProcessStep)description: Using a combination of Leica ALS60 and Optech Gemini LiDAR systems, 307 flight lines of high density data, at a nominal pulse spacing (NPS) of 1.5 meter, were collected over Maine (approximately 2327 square miles). Multiple returns were recorded for each laser pulse along with an intensity value for each return. A total of twenty-one (21) missions were flown April 18, 2012 May 12, 2012. Two airborne global positioning system (GPS) base stations were used in support of the LiDAR data acquisition. 34 ground control points were surveyed through static methods. The geoid used to reduce satellite derived elevations to orthometric heights was Geoid09. The horizontal datum used for this survey is North American Datum 1983 (NSRS2007), UTM19, and expressed in meters. The vertical datum used for this survey is North American Vertical Datum 1988 (NAVD88), and expressed in meters. Airborne GPS data was differentially processed and integrated with the post processed IMU data to derive a smoothed best estimate of trajectory (SBET). The SBET was used to reduce the LiDAR slant range measurements to a raw reflective surface for each flight line. System Parameters: - LIDAR data was collected using Leicas ALS60 and Optechs Gemini LiDAR Systems in Multi-Pulse mode. The ALS60 and Gemini LiDAR Systems collect up to four returns (echo) per pulse, recording attributes such as time stamp and intensity data, for the first three returns. If a fourth return was captured, the system does not record an associated intensity value. The aerial LiDAR was collected at the following sensor specifications: Nominal Post Spacing: 4.92 ft / 1.5 m, AGL (Above Ground Level) average flying height: 7,800 ft / 2,377 m (Leica ALS60), 6,800 ft / 2,072 m (Optech Gemini), MSL (Mean Sea Level) average flying height: Varies by terrain, Average Ground Speed: 150 knots / 172 mph, Field of View (full): 40 degrees, Pulse Rate: 99 kHz (Leica ALS60), 100 kHz (Optech Gemini), Scan Rate: 38 Hz (Leica ALS60), 32 Hz (Optech Gemini), Side Lap (Minimum): 25%.dateTime: DateTime: 2012-04-18T00:00:00processor: (CI_ResponsibleParty)organisationName: Woolpert, Inc.positionName: Geospatial ServicescontactInfo: (CI_Contact)phone: (CI_Telephone)voice: (937) 461-5660facsimile: (937) 461-0743address: (CI_Address)deliveryPoint: 4454 Idea Center Blvd.city: DaytonadministrativeArea: OHpostalCode: 45430country: USAhoursOfService: 8:00 a.m. to 5:00 p.m. Eastern Timerole: (CI_RoleCode) processorprocessStep: (LE_ProcessStep)description: The Leica ALS60 and Optech Gemini LiDAR system calibration and performance is verified on a periodic basis using Woolpert's calibration range. The calibration range consists of a large building and runway. The edges of the building and control points along the runway have been located using conventional survey methods. Inertial measurement unit (IMU) misalignment angles and horizontal accuracy are calculated by comparing the position of the building edges between opposing flight lines. The scanner scale factor and vertical accuracy is calculated through comparison of LiDAR data against control points along the runway. Field calibration is performed on all flight lines to refine the IMU misalignment angles. IMU misalignment angles are calculated from the relative displacement of features within the overlap region of adjacent (and opposing) flight lines. The raw LiDAR data is reduced using the refined misalignment angles.dateTime: DateTime: 2012-04-18T00:00:00processor: (CI_ResponsibleParty)organisationName: Woolpert, Inc.positionName: Geospatial ServicescontactInfo: (CI_Contact)phone: (CI_Telephone)voice: (937) 461-5660facsimile: (937) 461-0743address: (CI_Address)deliveryPoint: 4454 Idea Center Blvd.city: DaytonadministrativeArea: OHpostalCode: 45430country: USAhoursOfService: 8:00 a.m. to 5:00 p.m. Eastern Timerole: (CI_RoleCode) processorprocessStep: (LE_ProcessStep)description: Once the data acquisition and GPS processing phases are complete, the LiDAR data was processed immediately to verify the coverage had no voids. The GPS and IMU data was post processed using differential and Kalman filter algorithms to derive a best estimate of trajectory. The quality of the solution was verified to be consistent with the accuracy requirements of the project.dateTime: DateTime: 2012-05-14T00:00:00processor: (CI_ResponsibleParty)organisationName: Woolpert, Inc.positionName: Geospatial ServicescontactInfo: (CI_Contact)phone: (CI_Telephone)voice: (937) 461-5660facsimile: (937) 461-0743address: (CI_Address)deliveryPoint: 4454 Idea Center Blvd.city: DaytonadministrativeArea: OHpostalCode: 45430country: USAhoursOfService: 8:00 a.m. to 5:00 p.m. Eastern Timerole: (CI_RoleCode) processorprocessStep: (LE_ProcessStep)description: The individual flight lines were inspected to ensure the systematic and residual errors have been identified and removed. Then, the flight lines were compared to adjacent flight lines for any mismatches to obtain a homogenous coverage throughout the project area. The point cloud underwent a classification process to determine bare-earth points and non-ground points utilizing "first and only" as well as "last of many" LiDAR returns. This process determined bare-earth points (Class 2), noise (Class 7), water (Class 9) ignored ground (Class 10), unclassified data (Class 1), overlap points (Class 11). The bare-earth (Class 2 - Ground) LiDAR points underwent a manual QA/QC step to verify that artifacts have been removed from the bare-earth surface. The surveyed ground control points are used to perform the accuracy checks and statistical analysis of the LiDAR dataset.dateTime: DateTime: 2012-05-14T00:00:00processor: (CI_ResponsibleParty)organisationName: Woolpert, Inc.positionName: Geospatial ServicescontactInfo: (CI_Contact)phone: (CI_Telephone)voice: (937) 461-5660facsimile: (937) 461-0743address: (CI_Address)deliveryPoint: 4454 Idea Center Blvd.city: DaytonadministrativeArea: OHpostalCode: 45430country: USAhoursOfService: 8:00 a.m. to 5:00 p.m. Eastern Timerole: (CI_RoleCode) processorprocessStep: (LE_ProcessStep)description: Breaklines defining lakes, greater than two acres, and double-line streams, wider than 100 feet (30.5 meters), were compiled using digital photogrammetric techniques as part of the hydrographic flattening process and provided as ESRI Polyline Z and Polygon Z shape files. Breaklines defining water bodies and streams were compiled for this task order. The breaklines were used to perform the hydrologic flattening of water bodies, and gradient hydrologic flattening of double line streams. Lakes, reservoirs and ponds, at a nominal minimum size of two (2) acres or greater, were compiled as closed polygons. The closed water bodies were collected at a constant elevation. Rivers and streams, at a nominal minimum width of 100 feet (30.5 meters), were compiled in the direction of flow with both sides of the stream maintaining an equal gradient elevation. The hydrologic flattening of the LiDAR data was performed for inclusion in the National Elevation Dataset (NED).dateTime: DateTime: 2012-06-01T00:00:00processor: (CI_ResponsibleParty)organisationName: Woolpert, Inc.positionName: Geospatial ServicescontactInfo: (CI_Contact)phone: (CI_Telephone)voice: (937) 461-5660facsimile: (937) 461-0743address: (CI_Address)deliveryPoint: 4454 Idea Center Blvd.city: DaytonadministrativeArea: OHpostalCode: 45430country: USAhoursOfService: 8:00 a.m. to 5:00 p.m. Eastern Timerole: (CI_RoleCode) processorprocessStep: (LE_ProcessStep)description: The NOAA Coastal Services Center (CSC) received topographic files in LAS V1.2 format. The files contained lidar elevation measurements, intensity values, scan angle values, return information, and adjusted standard GPS time. The data were received in UTM Zone 19N, NAD83 coordinates and were vertically referenced to NAVD88 using the Geoid09 model. The vertical units of the data were meters. CSC performed the following processing for data storage and Digital Coast provisioning purposes: 1. Points in Class 11 (Overlap) were changed to Class 12 (Overlap). 2. The topographic las files were converted from orthometric (NAVD88) heights to ellipsoidal heights using Geoid09. 3. The topographic las files were converted from a Projected Coordinate System (UTM Zone 19N) to a Geographic Coordinate System (NAD83). 4. The topographic las files' horizontal units were converted from meters to decimal degrees. 5. The data were converted to LAZ format.dateTime: DateTime: 2013-10-01T00:00:00processor: (CI_ResponsibleParty)organisationName: DOC/NOAA/NOS/OCM > Office for Coastal Management, National Ocean Service, National Oceanic and Atmospheric Administration, U.S. Department of CommercecontactInfo: (CI_Contact)phone: (CI_Telephone)voice: 843-740-1200address: (CI_Address)deliveryPoint: 2234 South Hobson Ave.city: CharlestonadministrativeArea: SCpostalCode: 29405-2413electronicMailAddress: coastal.info@noaa.govonlineResource: (CI_OnlineResource)linkage: http://coast.noaa.govrole: (CI_RoleCode) processorprocessStep: (LE_ProcessStep)description: The NOAA National Geophysical Data Center (NGDC) received lidar data files via ftp transfer from the NOAA Coastal Services Center. The data are currently
being served via NOAA CSC Digital Coast at http://www.csc.noaa.gov/digitalcoast/. The data can be used to re-populate the system. The data are archived in LAS or LAZ format.
The LAS format is an industry standard for LiDAR data developed by the American Society of Photogrammetry and Remote Sensing (ASPRS); LAZ is a loseless compressed version of
LAS developed by Martin Isenburg (http://www.laszip.org/). The data are exclusively in geographic coordinates (either NAD83 or ITRF94). The data are referenced vertically to
the ellipsoid (either GRS80 or ITRF94), allowing for the ability to apply the most up to date geoid model when transforming to orthometric heights.dateTime: DateTime: 2013-11-19T00:00:00processor: (CI_ResponsibleParty)individualName: Mike SutherlandorganisationName: DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of CommercecontactInfo: (CI_Contact)phone: (CI_Telephone)voice: 303-497-6120facsimile: 303-497-6513address: (CI_Address)deliveryPoint: NOAA/NESDIS/NGDC E/GC1 325 Broadwaycity: BoulderadministrativeArea: COpostalCode: 80305-3328country: USAelectronicMailAddress: mike.sutherland@noaa.govhoursOfService: 7:30am-5:00pm Mountainrole: (CI_RoleCode) processorreturn to topmetadataMaintenance: (MD_MaintenanceInformation)maintenanceAndUpdateFrequency: (MD_MaintenanceFrequencyCode) annuallydateOfNextUpdate: 2014-11-19maintenanceNote: This metadata was automatically generated from the FGDC Content Standards for Digital Geospatial Metadata standard (version FGDC-STD-001-1998) using the 2013-01-04 version of the FGDC RSE to ISO 19115-2 for LiDAR transform.maintenanceNote: Translated from FGDC 2013-11-19T15:41:51.426-07:00return to topacquisitionInformation: (MI_AcquisitionInformation)instrument: (MI_Instrument)identifier: (MD_Identifier)code: Leica ALS60type: Light Detection and Rangingreturn to topacquisitionInformation: (MI_AcquisitionInformation)instrument: (MI_Instrument)identifier: (MD_Identifier)code: Optech Geminitype: Light Detection and Ranging